PROJECT SUMMARY This proposed project aims to develop a soft wearable transducer array for continuous, accurate, and non- invasive measurement of blood flow velocity waveforms. The blood flow velocity waveform can provide critical information about the major organ activities and psychiatric state changes, which would help raise patient awareness, assist preventive care, and serve as the basis for personalized medicine. Conventional measurement protocols include catheter implants, which is invasive and risky, and Doppler ultrasonography, which is heavily user-dependent and often has errors and artifacts. This research is distinct from the existing methods, because it offers several unique features. First, due to its low-profile form factors, the wearable ultrasonic device enables continuous measurement of the blood flow velocity waveform without constricting the natural movement of the subject. Second, this device has similar mechanical properties to the human skin and therefore can achieve a conformal and intimate contact with the skin, which allows accurate and stable measurements. Third, the phased array control mechanism facilitates focusing and steering the ultrasonic beam at any locations with predefined incident angles, which enhances the signal-to-noise-ratio and removes user errors for manual operations. Towards that end, by combining materials science, mechanical design, and electronics integration, we will use an iterative design of experiments to understand and optimize the performance of a single ultrasonic transducer. Then, we will develop phased array control mechanism on a wearable platform to achieve ultrasonic beam focusing and steering. After that, we will integrate the stretchable transducer array with the phased array control circuit to achieve continuous and accurate recording of blood flow velocity waveforms. The proposed research is the first of its kind to use a soft, stretchable system to diagnose and monitor deep tissues under the skin. The availability of a comfortable, non-invasive blood flow monitoring device will make a fundamental difference in how related diseases are diagnosed and treated, which will have a direct impact on the clinical practices. This wearable device will also shift the public perception of blood flow monitoring, promote preventive care, and provide unprecedented data streams for medical professionals, which will translate into significant reductions in associated mortality and healthcare costs. !